This invention relates to a vacuum die casting machine having an improved siphon tube and an associated method and more particularly to a siphon tube which is configured to reduce jetting in the shot cylinder of the vacuum die casting machine.
Vacuum die casting is a vacuum based method for producing metal parts by injection of liquid metal into a die using a piston and cylinder arrangement. Molten metal alloy, such as aluminum alloy, is drawn up by a siphon tube from a reservoir and into a shot cylinder by a vacuum. A piston is then used to rapidly inject the molten metal into a die.
A problem arises when metal build-up or necking in the siphon tube occurs as the liquid metal which is drawn from the metal reservoir freezes on the inside surface of the siphon tube. Excess build-up can lead to a phenomenon known as "jetting". Jetting occurs when the liquid metal, which is being forced through a small diameter, forms a jet of metal which impinges on the shot cylinder's top inside wall. This is a universally undesired result which leads to wear of the shot cylinder and the piston and repeated scraping of partially frozen material from the cylinder walls during each stroke.
Thus, there remains a need for an improved vacuum die casting machine which minimizes the effects of jetting in a simple and efficient manner.